1. Field of the Invention
The present invention relates to a novel process for producing aliphatic imines and/or amines, particularly those having a high molecular weight, from monohydric aliphatic alcohols and ether alcohols, particularly oxo alcohols having a high molecular weight, including dimer alcohols, as produced by the reaction of olefin feedstock in the oxo process. The oxo process involves the reaction of olefins with carbon monoxide and hydrogen to form predominantly aldehydes, which are converted to alcohols and other chemicals.
High molecular weight amines have a variety of utilities including the production of surfactants, wetting agents, intermediates, etc. However the production of such amines in high yield generally is difficult, requiring expensive catalyst systems and/or high temperatures and pressures.
2. Discussion of Prior Art
Processes for producing amines from aldehydes, ketones or alcohols, comprising reacting them with an aminating agent in the presence of a dehydrogenation catalyst, are well known. However many of the known processes are expensive, inefficient, inoperative for the production of high molecular weight and/or branched amines, and/or require harsh reaction conditions.
In most known processes for converting alcohols, particularly high molecular weight alcohols and branched alcohols, to amines by reaction with aminating agents such ammonia, it is difficult to obtain high selectivity, such as to primary amines. The amination product generally is a mixture of primary, secondary and tertiary amines. Also it is difficult to separate the formed amines, such as the primary amine, from the starting alcohol since the boiling points may be very similar or close. For example, the boiling points of 2-ethylhexanol and 2-ethylhexyl amine are similar so that separation by distillation means is difficult.
There is need for a simple and efficient process for selectively producing higher alkylated amines from olefin feedstock, such as from higher alkylated, branched or dimer alcohols produced from olefin feedstock by the oxo process. The generally-known reactions comprise converting the alcohol to the corresponding aldehyde by dehydrogenation, followed by aldol reaction and amination with suitable amines to form amines having high molecular weight alkyl substituents such as detergent range hydrophobe groups. Reference is made to PCT application WO 85-02173, published Aug. 23, 1985, for its disclosure of processes for the production of high molecular weight amines from aldehydes derived from olefin feedstock by the oxo process.
Reference is also made to U.S. Pat. Nos. 4,152,353; 4,210,605 and 4,480,131 and to European Patent Application 034,480 published Aug. 26, 1981, for their disclosure of other known processes for producing amines from alcohols by dehydrogenation in the presence of an amine, followed by amination. The generally-accepted reaction mechanism involves dehydrogenating the alcohol to the aldehyde, aminating to form an imine and hydrogenating the imine to form the desired amine.
However the aforementioned reaction mechanism is difficult to accomplish in high yield with certain reactants and catalyst systems for several reasons. Firstly, we have found that water must be removed continuously from the reaction medium, but this is difficult to accomplish in the presence of an amine since most amines are hygroscopic and resist separation of water therefrom. Secondly, the essential catalyst may react and/or become less soluble in the reaction medium as the conversion of the alcohol to the imine proceeds, thereby stopping the reaction before all of the alcohol has been converted, and reducing the yield of amine.
Another potential problem relates to the instability of the intermediate imine, which is a Schiff base and therefore undergoes aldol-dimerization and is susceptible to conversion to polymeric products even under relatively mild reaction conditions in the presence of certain catalysts.